Conventionally, there is known a technique of forming a hole in a processing target film by performing an etching process of etching the processing target film formed on a substrate. In this technique, the hole is extended, i.e., deeply etched, by performing the etching process. As the etching process progresses, however, a reaction product adheres to an inlet portion of the hole cumulatively. As a result, necking, which refers to a phenomenon by which the inlet portion of the hole is clogged with the reaction product, may occur.
To solve the problem, there is proposed a technique of removing the reaction product, which adheres to the inlet portion of the hole, in the middle of the etching process. For example, Patent Document 1 describes a technique of repeating a series of processes of stopping the etching process temporarily, selectively removing the reaction product adhering to the inlet portion of the hole, and then, resuming the etching process.
Patent Document 1: U.S. Pat. No. 7,547,636